1. Field of the Invention
The present invention relates to the structure of an output shaft for transmitting the output of an engine of a shaft driven vehicle to both the front wheel side and the rear wheel side of the vehicle.
2. Description of Background Art
One example of a structure of the output shaft, is disclosed in Japanese published unexamined patent application No. 2001-74027. The structure is divided into a shaft on the front wheel side and a shaft on the rear wheel side so that they can be separated or connected. The shaft on the front wheel side is supported via a needle bearing, and the shaft on the rear wheel side is supported via a ball bearing and a needle bearing respectively by a crankcase, whereby each shaft can be rotated. The shaft on the rear wheel side of the output shaft is sealed by an oil seal in a rear cover.
In the conventional type output shaft structure, since a bearing support of the output shaft is apart from the oil seal, the run-out of oil around the oil seal of the output shaft becomes large, and the sealing performance of the oil seal is unsatisfactory. Also, since the output shaft is divided into two, the structure is complex, the weight and cost are high, and the assembly is likely to be troublesome.
To solve the problems of the conventional type, a first aspect of the present invention is based upon the output shaft structure of a vehicle driven by shafts of an internal combustion engine and provides first and second cases mutually connected on a face perpendicular to a crankshaft and forming a crankcase, a case cover attached to the outside of the first case and an output shaft arranged in the crankcase and supported by a first bearing provided to the case cover and a second bearing provided to the first case. The output shaft includes a first large diameter part is positioned by touching it to the inside face of the first bearing and a second large diameter part is positioned by touching it to the outside face of the second bearing.
In view of the first aspect of present invention described above, since the output shaft includes the first large diameter part which is positioned by touching it to the inside face of the first bearing and the second large diameter part is positioned by touching it to the outside face of the second bearing, the output shaft can be attached from one direction after the first and second cases are connected. In addition, positioning can be easily and securely made. Also in recombination, a rear crankcase cover has only to be detached, and both assembly workability and maintainability are excellent.
A second aspect of the present invention is based upon the output shaft structure of a vehicle driven by shafts of an internal combustion engine and provides first and second cases mutually connected on a face perpendicular to a crankshaft and forming a crankcase, a case cover attached to the outside of the second case and an output shaft arranged in the crankcase and supported by a first bearing provided to the first case cover and a third bearing provided to the first case. Further, the output shaft includes first and second large diameter parts respectively positioned by touching them to each inside face of the first and second bearings.
In view of the second aspect of the present invention described above, since the first and second large diameter parts are respectively positioned by touching them to each inside face of the first and third bearings, positive effects similar to those achieved with the first aspect of the present invention can be produced.
A third aspect of the present invention is based upon the output shaft structure of a vehicle driven by shafts of an internal combustion engine and provides first and second cases mutually connected on a face perpendicular to a crankshaft and forming a crankcase, first and second case covers respectively attached to each outside of the first and second cases and an output shaft arranged in the crankcase and supported by first and third bearings respectively provided to the first and second case covers. Here again, the output shaft includes first and third large diameter parts positioned by touching them to each inside face of the first and third bearings.
In view of the third aspect of the present invention as described above, since the output shaft includes the first and second large diameter parts which are respectively positioned by touching them to each inside face of the first and third bearings, positive effects similar to those achieved in the first and second aspects the invention can again be produced. In this case, during recombination, the first case cover is detached.
A fourth aspect of the present invention is based upon the output shaft structure of a vehicle driven by shafts of an internal combustion engine and provides first and second cases mutually connected on a face perpendicular to a crankshaft and forming a crankcase, a case cover attached to the outside of the first case and an output shaft arranged in the crankcase and supported by a first bearing provided to the case cover and a second bearing provided to the first case. Also provided is an input gear for the output shaft which is arranged by touching an outside face of the second bearing. Further, the output shaft includes a first large diameter part positioned by touching it to the inside face of the first bearing and a second large diameter part positioned by touching it to the outside face of the input gear.
In view of the fourth aspect of the present invention described above, since the input gear to the output shaft is arranged by touching it to the outside face of the second bearing, and since the output shaft includes the first large diameter part positioned by touching it to the inside face of the first bearing and the second large diameter part positioned by touching it to the outside face of a bearing of the input gear, both the output shaft and the input gear can be easily and securely positioned.
A fifth aspect of the present invention is characterized in that the first bearing is a needle bearing and an oil seal is arranged close to the outside of the needle bearing. Therefore, according to this fifth aspect of the present invention, the run-out of oil from around the output shaft can be inhibited, and the sealing performance of the oil seal is improved.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.